Method and tool for router interface L2 redundancy

ABSTRACT

A method of router interface level 2 redundancy, and router implementing the method, including one or more of the following: starting redundant ports that are members of a level 2 redundancy group (L2RG) in a DOWN state; determining that none of the redundant ports are in an ACTIVE state; switching a first one of the redundant ports to an ACTIVE state; activating an Internet protocol interface for the L2RG; inserting an Internet protocol route for an interface subnet in an FIB of a router that contains the redundant ports; binding the Internet protocol route for the interface to the first one of the redundant ports; transitioning the first one of the redundant ports to a DOWN state; transitioning the Internet protocol interface to the DOWN state from an UP state; and removing the Internet protocol route for the interface from the FIB of the router.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to the field of Internet protocol (IP)routing.

2. Description of Related Art

IP routing denotes the set of protocols that determine the path thatdata follows in order to travel across multiple networks from its sourceto its destination. Data is routed from its source to its destinationthrough a series of routers, and across multiple networks. The IProuting protocols enable routers to build up a forwarding table thatcorrelates final destinations with next hop addresses.

When an IP packet is to be forwarded, a router uses its forwarding tableto determine the next hop for the packet's destination, based on thedestination IP address in the IP packet header, and forwards the packetappropriately. The next router then repeats this process using its ownforwarding table. This process is repeated until the packet reaches itsdestination. At each stage, the IP address in the packet header issufficient information to determine the next hop. No additional protocolheaders are required.

In computing and especially computer networks, a lag is a symptom whereresult of an action appears later than expected. While different kindsof latency are well defined technical terms, lag is the symptom, not thecause.

Latency is the time taken for a packet of data to be sent from oneapplication, travel to, and be received by another application. Thisincludes transit time over the network, and processing time at thesource and the destination computers. Specifically, this is the time forencoding the packet for transmission and transmitting it, the time forthat serial data to traverse the network equipment between the nodes,and the time to get the data off the circuit. This is also known asone-way latency. A minimum bound on latency is determined by thedistance between communicating devices and the speed at which the signalpropagates in the circuits. This is typically 70-95% of the speed oflight. Actual latency is usually much higher. This is due to packetprocessing in networking equipment, and other traffic.

While every packet experiences some amount of lag, the term lag istypically used to refer to delays that are noticeable to a user. Latencyis directly related to the physical distance that data travels. Thus,for example, the time taken for a packet to travel from a computerserver in Europe to a client in the same region is likely to be shorterthan the time to travel from Europe to the Americas or Asia. Protocolsand well written code that avoid unnecessary data transmissions are lessaffected by the latency inherent in a network. Modern corporate networkshave devices to cache frequently requested data and accelerateprotocols. This reduces application response time, the cumulative effectof latency.

In computer networking, the Address Resolution Protocol (ARP) is thestandard method for finding a host's hardware address when only itsnetwork layer address is known. ARP is not an IP-only or Ethernet-onlyprotocol. Rather, ARP can be used to resolve many differentnetwork-layer protocol addresses to hardware addresses. However, due tothe overwhelming prevalence of IPv4 and Ethernet, ARP is often used totranslate IP addresses to Ethernet MAC addresses.

ARP is also used for IP over other LAN technologies, such as Token Ring,FDDI, or IEEE 802.11, and for IP over ATM. ARP is used in four cases oftwo hosts communicating. These include 1) when two hosts are on the samenetwork and one desires to send a packet to the other; 2) when two hostsare on different networks and must use a gateway/router to reach theother host; 3) when a router needs to forward a packet for one hostthrough another router; and 4) when a router needs to forward a packetfrom one host to the destination host on the same network.

The first case is used when two hosts are on the same physical network,i.e. capable of directly communicating without the use of a router. Thelast three cases are the ones more often used over the Internet. This istrue because two computers connected to the Internet are typicallyseparated by a communications path consisting of more than three hops.

When one host wants to send data to another, the sending host needs adestination IP address for the receiving host. This is the network layeraddress. The IP address is found in the DNS server for a particular URL.The sending host also needs a layer 2 destination address for thereceiving host. This is a destination MAC address for the receivinghost. When a router lies between the sending host and the receivinghost, the router interface MAC address is used instead of the receivinghost MAC address. ARP is implemented to satisfy these requirements.

The foregoing objects and advantages of the invention are illustrativeof those that can be achieved by the various exemplary embodiments andare not intended to be exhaustive or limiting of the possible advantageswhich can be realized. Thus, these and other objects and advantages ofthe various exemplary embodiments will be apparent from the descriptionherein or can be learned from practicing the various exemplaryembodiments, both as embodied herein or as modified in view of anyvariation which may be apparent to those skilled in the art.Accordingly, the present invention resides in the novel methods,arrangements, combinations and improvements herein shown and describedin various exemplary embodiments.

SUMMARY OF THE INVENTION

Offering voice and video services over IP networks requires a highavailability of IP paths for IP routing within the IP networks.Accordingly, various exemplary embodiments include redundancy of IPpaths. Further, various exemplary embodiments incorporate such aredundancy on an access-link IP interface L2

In light of the present need for a method and tool for router interfaceL2 redundancy, a brief summary of various exemplary embodiments ispresented. Some simplifications and omission may be made in thefollowing summary, which is intended to highlight and introduce someaspects of the various exemplary embodiments, but not to limit itsscope. Detailed descriptions of a preferred exemplary embodimentadequate to allow those of ordinary skill in the art to make and use theinvention concepts will follow in later sections.

In various exemplary embodiments, redundant router IP interfaces includetwo or more IP interfaces with the same IP address (subnet), withdifferent MAC addresses and physical ports. In some such embodiments,the redundant router IP interfaces work in a combination of active andstandby modes and an activity status of an IP interface is determinedautomatically by monitoring ARP messages from neighboring nodes.

In other exemplary embodiments, one IP interface is associated with oneor more ports. In a simple example, one IP interface is associated withtwo ports. If any one port is in an operational UP state, the IPinterface state is UP. Thus, if all of the ports associated with the IPinterface are DOWN, the IP interface state is DOWN.

In connection with the foregoing, various exemplary embodiments includethe router interface L2 redundancy feature. In various exemplaryembodiments, this feature is used to allow IP nodes using gratuitous ARPL2 redundancy models to connect directly to a router.

Accordingly, various exemplary embodiments are useful for networksproviding highly available IP access interfaces. Examples of suchnetworks include, but are not limited to, voice over Internet protocol(VoIP), Internet protocol television (IPTV) regional and hub offices andother company offices, and so on.

Elaborating on the problems described above, there is often a problemconnecting an IP network element (NE) that uses redundant ports withgratuitous ARP L2 redundancy to an IP routed network. There are many IPNEs, such as VoIP gateways and servers, that use gratuitous ARP L2redundancy models. In such L2 redundancy models, the NE connects to arouter via two Ethernet links in active/standby status over a single IPsubnet.

In various exemplary embodiments, the NE tests the active Ethernet linkby pinging the interface IP address associated with the link. When alink failure is detected, the NE switches the activity status of bothlinks, thus toggling between the active and standby status. In variousexemplary embodiments, the NE broadcasts a gratuitous ARP reply afterthe activity switchover to announce the new MAC address of the newlyactive link for the interface IP after the switch.

It should be apparent that, based on the foregoing, various exemplaryembodiments include a pair of redundant Ethernet switching devices thatintermediate between the NE and the routers. In various exemplaryembodiments, such an Ethernet switching feature learns the MAC of the NEports and forwards traffic according to the MAC address in the Ethernetframe. This is true because both ports have the same IP address.

Some current embodiments consist of deploying redundant Ethernetswitches to interconnect an NE using redundant ports with L2 redundancyto the IP router. Some such embodiments are directly targeted towardssolving the problems described above. In some such embodiments, upon afailure, the gratuitous ARP triggers ARP learning on the router toregister a new MAC address against the IP address previously in use.

In various exemplary embodiments, the new IP traffic uses the new MACaddress, and the redundant Ethernet switches with the MAC learning todirect traffic automatically to the correct port based on thedestination MAC addresses in the Ethernet frames. However, suchembodiments necessitate infrastructure expenses for the redundantEthernet switches. Accordingly, various exemplary embodiments overcomethis problem by eliminating the expense for redundant Ethernet switches.

Other current embodiments solve the foregoing problems using linkaggregation control protocol (LACP) between the NE and the router.However, such embodiments are currently uncommon, though they may becomecommon in the future.

Accordingly, various exemplary are a method of router interface level 2redundancy, and router implementing the method, including one or more ofthe following: starting redundant ports that are members of a level 2redundancy group (L2RG) in a DOWN state; determining that none of theredundant ports are in an ACTIVE state; switching a first one of theredundant ports to an ACTIVE state; activating an Internet protocolinterface for the L2RG; inserting an Internet protocol route for aninterface subnet in an FIB of a router that contains the redundantports; binding the Internet protocol route for the interface to thefirst one of the redundant ports; transitioning the first one of theredundant ports to a DOWN state; transitioning the Internet protocolinterface to the DOWN state from an UP state; and removing the Internetprotocol route for the interface from the FIB of the router.

Various exemplary embodiments also include one or more of the following:determining that first one of the redundant ports is in the ACTIVEstate; switching the first one of the redundant ports to a STANDBYstate; receiving a gratuitous address resolution protocol reply;transitioning a second one of the redundant ports of the level 2redundancy group from the STANDBY state to the ACTIVE state;transitioning the first one of the redundant ports to the STANDBY state;changing a binding of the Internet protocol route from the first one ofthe redundant ports to the second one of the redundant ports; anddisassociating the binding of the Internet protocol route from the firstone of the redundant ports and associating the binding of the Internetprotocol route with the second one of the redundant ports.

Various exemplary embodiments also include one or more of the following:connecting an Internet protocol node directly to an Internet protocolrouting device; establishing one Internet protocol interface having oneInternet protocol subnet; establishing the level 2 redundancy group witha plurality of different ports that are the redundant ports; and usinggratuitous address resolution protocol level 2 redundancy to connect theInternet protocol node directly to the Internet protocol routing device.

In various exemplary embodiments the first one of the redundant portstransitions to the DOWN state upon a physical link failure causing aloss of signal or upon an administrative command for the first one ofthe redundant ports to transition to the DOWN state; and the Internetprotocol interface is transitioned to the DOWN state upon adetermination that all of the redundant ports of the level 2 redundancygroup are in the DOWN state, or upon an administrative command that theinterface state transition to the DOWN state.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to better understand various exemplary embodiments, referenceis made to the accompanying drawings, wherein:

FIG. 1 is a schematic diagram of the first exemplary embodiment of arouter for use in a system for router interface level two redundancy;

FIG. 2 is a schematic diagram of a second exemplary embodiment of arouter for use in a system for router interface level two redundancy;

FIG. 3 is a schematic diagram of a third exemplary embodiment of arouter for use in a system for router interface level two redundancy;

FIG. 4 is an exemplary embodiment of a port state diagram for use inconnection with a system and method for router interface level tworedundancy;

FIG. 5 is an exemplary embodiment of an interface state diagram for usein connection with a system and method for router interface level tworedundancy;

FIG. 6 is a flow chart of a method for connecting IP NEs to an IP routednetwork through an Ethernet switched network;

FIG. 7 is a flow chart of an exemplary embodiment of a method for routerinterface level two redundancy; and

FIG. 8 is a flow chart of a continuation of the method of FIG. 7.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

Referring now to the drawings, in which like numerals refer to likecomponents or steps, there are disclosed broad aspects of variousexemplary embodiments.

FIG. 1 is a schematic diagram of the first exemplary embodiment of arouter 100 for use in a system for router interface level tworedundancy. The router 100 is a modular router and includes a controlcard 110, a line card #1, a line card #2 and a line card #n. Line card#n is intended to represent that, in various exemplary embodiments, themodular router 100 includes any number of line cards.

Control card 110 includes layer 2 redundancy group (L2RG) system controlmodule 120. Similarly, line card #1 includes L2RG member controlinstance #1. Line card #2 includes L2RG member control instance #2, andline card #n includes L2RG member control instance #n.

Control messaging path 130 passes between L2RG member control instance#1 and L2RG system control module 120. Similarly, control messaging path140 passes between L2RG member control instance #2 and L2RG systemcontrol module 120. Likewise, control messaging path 150 passes betweenL2RG member control instance #n and L2RG system control module 120. Theoperation of the various elements in modular router 100 will bediscussed in greater detail below in connection with other Figures.

FIG. 2 is a schematic diagram of a second exemplary embodiment of arouter 200 for use in a system for router interface level tworedundancy. Router 200 is a modular router. Modular router 200 includesline card #1 with L2RG member control instance #1, line card #2 withL2RG member control instance #2 and line card #n with L2RG membercontrol instance #n just as with modular router 100. The primarydifference between modular router 200 and modular router 100 is that thecontrol card 110 is duplicated into two cards in modular router 200 forredundance. Thus, modular router 200 includes control card A and controlcard B.

Control card A includes L2RG system control module A. Similarly, controlcard B includes L2RG system control module B. The combination of L2RGsystem control module A and L2RG system control module B functions thesame as L2RG system control module 120. Thus, the functions attributedto the system control module elsewhere herein are performedalternatively in various exemplary embodiments by a single systemcontrol module such as L2RG system control module 120 or by a systemcontrol module broken into multiple components such as the combinationof L2RG system control module A and L2RG system control module B.

Because the combination of L2RG system control module A and L2RG systemcontrol module B functions as L2RG system control module 120, inexemplary modular router 200 each of L2RG member control instance #1,L2RG member control instance #2 and L2RG member control instance #n havea control messaging path to each of L2RG system control module A andL2RG system control module B. However, it should be apparent that, invarious exemplary embodiments, the functions attributed to the systemcontrol module herein are accomplished as long as each member controlinstance is in control messaging communication with at least one portionof the system control module. In other words, it should be apparentthat, in embodiments where the system control module is broken intomultiple components as with modular router 200, it is not absolutelynecessary that each member control instance be in direct communicationwith each portion of the system control module.

As depicted in connection with modular router 200, L2RG member controlinstance #1 has control messaging path 210 to L2RG system control moduleA and control messaging path 220 to L2RG system control module B.Likewise, L2RG member control instance #2 has control messaging path 230to L2RG system control module A and control messaging path 240 to L2RGsystem control module B. L2RG member control instance #n has controlmessaging path 250 to L2RG system control module B and control messagingpath 260 to L2RG system control module A. As with modular router 100,the functions performed by the various components of modular router 200are discussed elsewhere herein.

FIG. 3 is a schematic diagram of a third exemplary embodiment of arouter 300 for use in a system for router interface level tworedundancy. Exemplary router 300 is a non-modular router. Thus,non-modular router 300 includes router card 310. Because router 300 is anon-modular router, it does not include a plurality of line cards.Rather, L2RG system control module 320 within router card 310 performsfor all of the functions of the member control instances and systemcontrol modules in modular router 100 and modular router 200.

Thus, L2RG system control module 320 includes not only all of thefeatures of L2RG system control module 120, but also all of L2RG membercontrol instance #1, L2RG member control instance #2 and L2RG membercontrol instance #n. Each of these components are in self containedcontrol messaging communication with one another within system controlmodule 320 on router card 310 of non-modular router 300.

Accordingly, it should be apparent that all of the functions describedelsewhere herein are performed by any of modular router 100, modularrouter 200 and non-modular router 300. No limitations exist restrictingthe performance of the various functions described elsewhere herein toany one or subset of modular router 100, modular router 200 andnon-modular router 300. Rather, any of modular router 100, modularrouter 200 and non-modular router 300 are selected in various exemplaryembodiments to perform any of the functions described herein.

Accordingly, various exemplary embodiments implement a redundant orsingle router interface control module to monitor ARP activity on tworedundant IP interfaces or a single IP interface having the same IPsubnet on two different ports. This is used to control the activitystatus of the two different ports and for binding the subnet IP route tothe active port. This is described in greater detail in connection withFIGS. 4-8 below.

FIG. 4 is an exemplary embodiment of a port state diagram 400 for use inconnection with a system and method for router interface level tworedundancy. Exemplary port state diagram 400 depicts three states forports of router 100, router 200, router 300 that are a part of the L2RG.Those three states are DOWN 405, STANDBY 410 and ACTIVE 415.

The redundant ports in router 100, 200,300 that are part of the L2RG(redundant router IP interface group or R2I2G) start in the DOWN 405state. A port of router 100, 200, 300 that is part of the L2RG thentransitions to STANDBY 410 via transition path 420 during aninitialization procedure. Such an initialization procedure is referredto in state diagram 400 as ADMIN UP.

A port of router 100, 200, 300 transitions back to the DOWN 405 statevia transition path 425 upon one of two occurrences. First, a port ofrouter 100, 200, 300 transitions from STANDBY 410 to DOWN 405 viatransition path 405 when it is deliberately configured to go DOWN. Thisis referred to in state diagram 400 as ADMIN DOWN.

The other condition upon which a port of router 100, 200, 300 that ispart of the L2RG transitions from STANDBY 410 to DOWN 405 via transitionpath 425 occurs when the port becomes operationally DOWN. A port becomesoperationally DOWN when the port gets cut, a link associated with theport gets cut, a fiber necessary for communications from the port getscut, and so on.

A port of router 100, 200, 300 that is part of the L2RG transitions fromSTANDBY 410 to ACTIVE 415 via transition path 430. Transition path 430is followed upon one of two conditions. First, a port of router 100,200, 300 that is part of the L2RG transitions from STANDBY 410 to ACTIVE415 via transition path 430 when a gratuitous ARP is received. The othercondition upon which transition path 430 is followed occurs when thereis no other ACTIVE port in the L2RG.

A port in router 100, 200, 300 that is part of the L2RG transitions fromACTIVE 415 to STANDBY via transition path 435. Transition path 435 isfollowed when a gratuitous ARP is received by a different port of router100, 200, 300 that is part of the L2RG and is in the STANDBY 410 state.Transition paths 430 and 435 are followed in tandem by two ports of theL2RG.

In the ACTIVE 415 state, IP communication proceeds over the ACTIVE IPport as usual. When transitions are occurring between STANDBY 410 andACTIVE 415, the STANDBY port transitions into ACTIVE 415 state and thepreviously ACTIVE port transitions to the STANDBY 410 state.Accordingly, the associated subnet IP router binding is switched fromthe old ACTIVE port to the new ACTIVE port. Accordingly, it should beunderstood that this association of the subnet router with the ACTIVEport occurs at the end of transition 430. Similarly, at the end oftransition 435, the subnet route binding is disassociated from the portentering STANDBY state 410.

A port of router 100, 200, 300 that is in the L2RG transitions fromACTIVE state 415 directly to DOWN state 405 via transition path 440.This transition occurs upon one of two conditions. First, a porttransitions along transition path 440 when it is administrativelyconfigured to do so as indicated by ADMIN DOWN. Second, a porttransitions along transition path 440 if the port is operationally DOWN.This was discussed above in connection with transition path 425 and isindicated in connection with transition path 440 as PORT DOWN. Inaddition to the description above in connection with transition path425, an operationally DOWN port can be thought of as a loss of signal(LOS) corresponding to a physical failure of a link. At the end oftransition path 440, the subnet route binding is disassociated from theport entering the DOWN state 405.

The port states 405, 410, 415 and the transitions there between 420,425, 430, 435, 440 are controlled by the system control module. Asdescribed above, the configurable port priority attribute is used forpreempting an ACTIVE port with a STANDBY port and causing a manualswitch between the ACTIVE port and the STANDBY port. Accordingly, itshould be apparent that the L2RG consists of at least two ports.However, it should also be apparent that, in various exemplaryembodiments, the L2RG consists of more than two ports.

Likewise, in various exemplary embodiments, all of the plurality ofports in the L2RG reside on a single line card. However, in otherexemplary embodiments, the plurality of ports in the L2RG reside on aplurality of line cards. In fact, in various exemplary embodiments, onlyone port of the L2RG resides on each line card. Thus, in suchembodiments, the number of line cards with ports in the L2RG is equal tothe number of ports in the L2RG.

The foregoing state transitions depicted in port state diagram 400 willnow be described in connection with a simple example. In this example,L2RG member control instance #1 and L2RG member control instance #2 haveports in the same L2RG. The port of L2RG member control instance #1 thatis part of the L2RG is in an ACTIVE state 415. The port in L2RG membercontrol instance #2 that is part of the L2RG is in a STANDBY state 410.

A gratuitous ARP is received by the port of L2RG member control instance#2 that is part of the L2RG. Then, L2RG member control instance #2communicates with the system control module via a control messaging pathor paths that the gratuitous ARP has been received and sends aninstruction to deactivate the ACTIVE port.

In response to this communication received from L2RG member controlinstance #2 by the system control module, the system control moduletransitions the port of L2RG member control instance #1 that is part ofthe L2 RG from ACTIVE state 415 to STANDBY state 410 via transition path435. Likewise, at that time the port in L2 RG member control instance #2that is part of the L2 RG transitions from STANDBY state 410 to ACTIVEstate 415 via transition path 430. Accordingly, the system controlmodule controls the states of the ports in the L2 RG.

FIG. 5 is an exemplary embodiment of an interface state diagram 500 foruse in connection with a system and method for router interface leveltwo redundancy. The interface state diagram 500 has two states. The twostates of the interface state diagram 500 are DOWN 505 and UP 510. Theinterface begins in the DOWN state 505.

The interface transitions from a DOWN state 505 to the UP state 510 viatransition path 515. Transition path 515 is followed when two conditionsare satisfied. Those two conditions are that the interface has beenadministratively configured to be in an UP state, indicated as ADMIN UPand at least one of L2 RG ports is in an ACTIVE state 415. When thesetwo conditions are satisfied and transition path 515 is followed for theadministrative state, an IP interface subnet route binding is added atthe end of transition path 515. The IP interface subnet is inserted inthe FIB of router 100, 200, 300 and bound to the port of the L2 RG inthe ACTIVE state 415.

The administrative state transitions from UP 510 to DOWN 505 viatransition path 520. Transition path 520 is followed when either of theconditions necessary for transition path 515 are no longer true. Thus,transition path 520 is followed when an administrative instruction issent to transition to the DOWN state 505, represented as ADMIN DOWN orwhen all of the ports in the L2 RG are in the DOWN state 405. At the endof transition path 520, the IP interface subnet route binding isremoved.

Based on the foregoing, there are three aspects of the subject matterdescribed herein. First, the L2 RG is created from two or more ports.Second, the state of the ports in the L2 RG are controlled by the systemcontrol module according to port state diagram 400. Third, the state ofthe IP interface that uses the L2 RG is controlled by the control moduleaccording to interface state diagram 500. The implementation of thislarger overview according to various exemplary embodiments will now bedescribed in connection with FIGS. 6-8.

FIG. 6 is a flow chart of a method 600 for connecting IP NEs to an IProuted network through an Ethernet switched network. The method 600starts in step 610 and continues to step 620.

In step 620, two Ethernet links are established over one IP subnet. Oneof the two established Ethernet links is in a STANDBY status or state,and the other of the two established Ethernet links is in an ACTIVEstatus or state.

Following step 620, the method 600 proceeds to step 630. In step 630, anetwork element (NE) is connected to a router via the ACTIVE Ethernetlink established in step 620. In various exemplary embodiments, thenetwork element is a server. In other exemplary embodiments, the networkelement is a voice over Internet protocol “VoIP” gateway. A server and aVoIP gateway are examples of NEs. Thus, it should be understood thatthere are many other examples of elements that function as networkelements as that term is used herein.

In step 640, the NE pings an associated interface IP address to test theACTIVE Ethernet link established in step 620. Following step 640, themethod 600 proceeds to step 650.

In step 650, a failure of the ACTIVE Ethernet link is detected.Following step 650, the method 600 proceeds to step 660.

In step 660, the NE switches the activity statuses of the two Ethernetlinks established in step 620. Thus, in step 660, the ACTIVE Ethernetlink becomes a STANDBY Ethernet link, and the STANDBY Ethernet linkbecomes an ACTIVE Ethernet link.

In step 670, a gratuitous ARP reply is broadcast by the NE. Followingstep 670, the method 600 proceeds to step 680.

The newly active Ethernet link in the broadcast of step 670 has a newMAC address. In step 680 this new MAC address is announced. Followingstep 680, the method 600 proceeds to step 690 where the method 600stops.

FIG. 7 is a flow chart of an exemplary embodiment of a method 700 forrouter interface level two redundancy. Method 700 starts in step 702 andproceeds to step 704.

In step 704, an IP node is directly connected to an IP routing device.In various exemplary embodiments, step 704 is accomplished usinggratuitous ARP L2 redundancy.

In step 706, one IP interface having one IP subnet is established. Instep 708, an L2RG of two different ports is also established. Once theL2RG is set up in this manner, the transitions described above inconnection with the state diagram 400 and state diagram 500 begin.Accordingly, in step 710, all of the redundant ports to be part of theL2RG are started in a DOWN state 405 as members of the L2RG.

Next, after the L2RG begins functioning, an evaluation is made whetherany of the redundant ports that are members of the L2RG are in an ACTIVEstate. When a determination is made in step 712 that one of the ports inthe L2RG is in an ACTIVE state 415, the method 700 proceeds to step 724in FIG. 8 as indicated by transitional element A.

When a determination is made in step 712 that none of the ports that aremembers of the L2RG are in an ACTIVE state 415, the method 700 proceedsto step 714. In step 714, one of the ports in the L2RG is switched toACTIVE state 415. Correspondingly, in step 716, the IP interface isactivated. Thus, in step 716, the interface state transitions from DOWN505 to UP 510 via transition path 515.

Accordingly, in step 718, the IP route for the interface subnet isinserted in the router FIB. Likewise, in step 720, the IP route for theinterface is bound to the ACTIVE IP port in the L2RG. Following step720, method 700 proceeds to step 734 via transitional element B. Thiswill be discussed in greater detail below in connection with FIG. 8.

FIG. 8 is a flow chart 722 of a continuation of the method 700 of FIG.7. Flow chart 722 begins in step 724. Step 724 is reached, as mentionedabove, via transitional element A when a determination is made in step712 that the L2RG has a port in the ACTIVE state 415.

In step 724, the port in the L2RG that is in the ACTIVE state 415 isswitched to the STANDBY state 410 via transition path 435. Accordingly,instep 726, the gratuitous ARP reply is received. Likewise, in step 728,the port in the L2RG in the STANDBY state 410 is transitioned to theACTIVE state 415 via transition path 430.

Accordingly, in step 730, the previously ACTIVE port is transitionedfrom ACTIVE 415 to STANDBY 410 via transition path 435. Thus, asdiscussed above, at the end of transition path 435, the IP route bindingis disassociated from the port transitioning from ACTIVE 415 to STANDBY410 and associated with the port transitioning from STANDBY 410 toACTIVE 415.

In step 734, the ACTIVE port is transitioned from ACTIVE state 415 toDOWN state 405 via transition path 440. As discussed above, step 734occurs when there is a physical link failure (LOS). Step 734 also occursupon execution of an administrative command for such a transition.

In step 736 a determination is a made that all ports in the L2RG are inthe DOWN state 405. As described above in connection with transitionpath 520, when the determination of step 736 is made, the IP interfacestate is transitioned from UP 510 to DOWN 505 in step 738. The IPinterface state is also transitioned from UP to DOWN 505 in step 738upon an administrative command for such a state change to occur.

In step 740, the IP route for the interface subnet is removed from therouter FIB. This was also described above as the removal of the IPinterface subnet route binding in connection with transition path 520.Following step 740, the method 700 proceeds to step 742 where the method700 stops.

Based on the foregoing, various exemplary embodiments eliminate the needto purchase redundant Ethernet switches in order to offer level 2 style(gratuitous ARP) redundancy between an NE and a router. Accordingly,various exemplary embodiments save network operators the expense ofredundant Ethernet switches and associated components to offer level 2style redundancy to VoIP gateways and other servers in a networkoperator's corporate office for other centralized operational location.Accordingly, it is believed that various exemplary embodiments will savecertain corporations a significant quantity of money.

Although the various exemplary embodiments have been described in detailwith particular reference to certain exemplary aspects thereof, itshould be understood that the invention is capable of other differentembodiments, and its details are capable of modifications in variousobvious respects. As is readily apparent to those skilled in the art,variations and modifications can be affected while remaining within thespirit and scope of the invention. Accordingly, the foregoingdisclosure, description, and figures are for illustrative purposes only,and do not in any way limit the invention, which is defined only by theclaims.

1. A method of router interface level 2 redundancy, comprising: startingredundant ports that are members of a level 2 redundancy group in a DOWNstate; determining that none of the redundant ports that are members ofthe level 2 redundancy group are in an ACTIVE state; switching a firstone of the redundant ports that are members of the level 2 redundancygroup to an ACTIVE state; activating an Internet protocol interface forthe level 2 redundancy group; inserting an Internet protocol route foran interface subnet in an FIB of a router that contains the redundantports that are members of the level 2 redundancy group; binding theInternet protocol route for the interface to the first one of theredundant ports; transitioning the first one of the redundant ports to aDOWN state; transitioning the Internet protocol interface to the DOWNstate from an UP state; and removing the Internet protocol route for theinterface from the FIB of the router.
 2. The method of router interfacelevel 2 redundancy, according to claim 1, further comprising:determining that first one of the redundant ports is in the ACTIVEstate; switching the first one of the redundant ports to a STANDBYstate; receiving a gratuitous address resolution protocol reply;transitioning a second one of the redundant ports of the level 2redundancy group from the STANDBY state to the ACTIVE state;transitioning the first one of the redundant ports to the STANDBY state;and changing a binding of the Internet protocol route from the first oneof the redundant ports to the second one of the redundant ports.
 3. Themethod of router interface level 2 redundancy, according to claim 2,further comprising disassociating the binding of the Internet protocolroute from the first one of the redundant ports and associating thebinding of the Internet protocol route with the second one of theredundant ports.
 4. The method of router interface level 2 redundancy,according to claim 1, further comprising: connecting an Internetprotocol node directly to an Internet protocol routing device;establishing one Internet protocol interface having one Internetprotocol subnet; and establishing the level 2 redundancy group with aplurality of different ports that are the redundant ports.
 5. The methodof router interface level 2 redundancy, according to claim 4, whereinconnecting the Internet protocol node directly to the Internet protocolrouting device is accomplished using gratuitous address resolutionprotocol level 2 redundancy.
 6. The method of router interface level 2redundancy, according to claim 1, wherein the first one of the redundantports transitions to the DOWN state upon a physical link failure causinga loss of signal.
 7. The method of router interface level 2 redundancy,according to claim 1, wherein the first one of the redundant portstransitions to the DOWN state upon an administrative command for thefirst one of the redundant ports to transition to the DOWN state.
 8. Themethod of router interface level 2 redundancy, according to claim 1,wherein the Internet protocol interface is transitioned to the DOWNstate upon a determination that all of the redundant ports of the level2 redundancy group are in the DOWN state.
 9. The method of routerinterface level 2 redundancy, according to claim 1, wherein the Internetprotocol interface state is transitioned to the DOWN state upon anadministrative command that the interface state transition to the DOWNstate.
 10. A router for router interface level 2 redundancy, comprising:means for starting redundant ports that are members of a level 2redundancy group in a DOWN state; means for determining that none of theredundant ports that are members of the level 2 redundancy group are inan ACTIVE state; means for switching a first one of the redundant portsthat are members of the level 2 redundancy group to an ACTIVE state;means for activating an Internet protocol interface for the level 2redundancy group; means for inserting an Internet protocol route for aninterface subnet in an FIB of a router that contains the redundant portsthat are members of the level 2 redundancy group; means for binding theInternet protocol route for the interface to the first one of theredundant ports; means for transitioning the first one of the redundantports to a DOWN state; means for transitioning the Internet protocolinterface to the DOWN state from an UP state; and means for removing theInternet protocol route for the interface from the FIB of the router.11. The router for router interface level 2 redundancy, according toclaim 10, further comprising: means for determining that first one ofthe redundant ports is in the ACTIVE state; means for switching thefirst one of the redundant ports to a STANDBY state; means for receivinga gratuitous address resolution protocol reply; means for transitioninga second one of the redundant ports of the level 2 redundancy group fromthe STANDBY state to the ACTIVE state; means for transitioning the firstone of the redundant ports to the STANDBY state; and means for changinga binding of the Internet protocol route from the first one of theredundant ports to the second one of the redundant ports.
 12. The routerfor router interface level 2 redundancy, according to claim 11, furthercomprising means for disassociating the binding of the Internet protocolroute from the first one of the redundant ports and means forassociating the binding of the Internet protocol route with the secondone of the redundant ports.
 13. The router for router interface level 2redundancy, according to claim 10, further comprising: means forconnecting an Internet protocol node directly to an Internet protocolrouting device; means for establishing one Internet protocol interfacehaving one Internet protocol subnet; and means for establishing thelevel 2 redundancy group with a plurality of different ports that arethe redundant ports.
 14. The router for router interface level 2redundancy, according to claim 13, wherein the means for connecting theInternet protocol node directly to the Internet protocol routing device15. The router for router interface level 2 redundancy, according toclaim 10, wherein the first one of the redundant ports transitions tothe DOWN state upon a physical link failure causing a loss of signal.16. The router for router interface level 2 redundancy, according toclaim 10, wherein the first one of the redundant ports transitions tothe DOWN state upon an administrative command for the first one of theredundant ports to transition to the DOWN state.
 17. The router forrouter interface level 2 redundancy, according to claim 10, wherein theInternet protocol interface is transitioned to the DOWN state upon adetermination that all of the redundant ports of the level 2 redundancygroup are in the DOWN state.
 18. The router for router interface level 2redundancy, according to claim 10, wherein the Internet protocolinterface state is transitioned to the DOWN state upon an administrativecommand that the interface state transition to the DOWN state.